# ASAS 2009 Axial Spondyloarthritis Classification Calculator

> ASAS 2009 Axial Spondyloarthritis Classification Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Applies the ASAS 2009 axial spondyloarthritis classification criteria (Rudwaleit set 3a) via imaging and clinical arms to determine if a patient meets criteria for axial SpA classification.

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/asas_axial_spa
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/asas-2009-axial-spondyloarthritis-classification-calculator-702d2cd5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BnRALc1qWxqgn4AHMoPAm

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability asas-2009-axial-spondyloarthritis-classification-calculator-702d2cd5
```

Example prompt: My patient has had chronic back pain for over 3 months with onset at age 32. MRI shows sacroiliitis, and they also have a positive HLA-B27, inflammatory back pain, and a history of uveitis. Can you run the ASAS 2009 axial SpA classification — no radiographic sacroiliitis, no arthritis, no enthesitis, no dactylitis, no psoriasis, no IBD, good NSAID response, no family history, and elevated CRP?

## When to prefer this

Use this endpoint when you need to apply specifically the ASAS 2009 axial SpA classification criteria (Rudwaleit, set 3a / fig 2) — covering both the imaging arm and the clinical HLA-B27 arm — for patients with chronic back pain of ≥3 months and onset before age 45. Do not use for peripheral SpA (use ASAS 2011 peripheral criteria instead), modified New York criteria for AS only, or any case requiring actual radiology reading or laboratory HLA-B27 assay, which must be supplied by the caller.

## Known failure modes

- Missing required boolean parameters (e.g. chronic_back_pain_ge_3_months, hla_b27) returns a validation error
- Age at onset ≥45 or chronic back pain <3 months causes entry criteria failure — patient is not classifiable
- HLA-B27 false with no imaging findings means neither arm can be satisfied
- Caller misassigning clinical findings (e.g. counting HLA-B27 as one of the two required clinical arm SpA features) will yield incorrect results — the API enforces that HLA-B27 is obligatory but does not count toward the two other features
- Peripheral ASAS 2011 criteria or modified New York AS-only criteria cannot be applied by this endpoint

## How this service works

ASAS 2009 axial SpA classification (Rudwaleit set 3a / fig 2). Required: chronic back pain ≥3 months and age at onset <45. Imaging arm: MRI or modified New York sacroiliitis plus ≥1 of 11 SpA features. Clinical arm: HLA-B27 plus ≥2 other features (HLA-B27 does not count toward those two). Not a diagnosis. Not peripheral ASAS 2011. Not modified New York AS-only. magent does not read films or assay HLA-B27.

## Output

Returns a structured result indicating whether the patient meets ASAS 2009 axial SpA classification criteria, specifying which arm (imaging or clinical) was satisfied, the count of SpA features present, and the logical breakdown of each arm's criteria evaluation. This is a classification tool, not a clinical diagnosis.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "headers": {
     "type": "object",
     "additionalProperties": {
      "type": "string"
     }
    },
    "queryParams": {
     "type": "object",
     "required": [
      "chronic_back_pain_ge_3_months",
      "age_at_onset_years",
      "mri_sacroiliitis",
      "radiographic_sacroiliitis",
      "inflammatory_back_pain",
      "arthritis",
      "enthesitis_heel",
      "uveitis",
      "dactylitis",
      "psoriasis",
      "ibd",
      "nsaid_good_response",
      "family_history_spa",
      "hla_b27",
      "elevated_crp"
     ],
     "properties": {
      "ibd": {
       "type": "boolean",
       "description": "Past or present Crohn's disease or ulcerative colitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not diagnose IBD."
      },
      "hla_b27": {
       "type": "boolean",
       "description": "HLA-B27 positive as assigned by the caller (Rudwaleit 2009). Obligatory for the clinical arm; does not count toward the two other SpA features. Counts toward spa_feature_count and the imaging arm. true or false. magent does not assay HLA-B27."
      },
      "uveitis": {
       "type": "boolean",
       "description": "Past or present uveitis confirmed by an ophthalmologist, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine the eye."
      },
      "arthritis": {
       "type": "boolean",
       "description": "Past or present synovitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine joints."
      },
      "psoriasis": {
       "type": "boolean",
       "description": "Past or present psoriasis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine skin."
      },
      "dactylitis": {
       "type": "boolean",
       "description": "Past or present dactylitis diagnosed by a physician, as assigned by the caller (Rudwaleit 2009). true or false. magent does not examine digits."
      },
      "elevated_crp": {
       "type": "boolean",
       "description
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/asas-2009-axial-spondyloarthritis-classification-calculator-702d2cd5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)